Bipolar jets in planetary nebulae: An analytical model |
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| Authors: | G Pascoli |
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| Institution: | (1) Department of Physics, Faculté des Sciences, 33, rue Saint-Leu, F-80039 Amiens Cedex, France |
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| Abstract: | The various and hitherto partially unsolved problems relative to the origin of bipolar jets or highly collimated fast outflows
in planetary nebulae are reviewed within the framework of a stationary magnetohydrodynamic model.
In order to explain the observations of high polar velocities and the presence of polar blobs or knots in planetary nebulae,
theoretical models are proposed taking into account both a large scale azimuthal magnetic field and an anisotropic turbulent
velocity field.
The models predict equatorial-to-polar density ratios which are rather small, in the range 2 to 3. Conversely, the polar-to-equatorial
velocity contrasts are higher, with typical values upto 10. Thus thead hoc hypothesis implicit in the literature that the density contrast is varying in inverse ratio to the velocity one, does not
seem well adapted to the bipolar jet phenomenon in planetary nebulae.
We point out, therefore, that the bipolar jets have to be considered as a transient aspect of a very complex phenomenon. The
model can be applied to objects such as He 2–104 or Mz3, M2–9. |
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| Keywords: | Planetary nebula bipolar magnetic field |
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